1. Field of the Invention
The invention generally relates to coatings for metals and refractory materials. More specifically, the invention relates to coatings for metals and refractory materials that provide improved heat and wear resistance to the coated material.
2. Description of the Relevant Art
Metals and refractory materials are used in many applications that involve high temperatures, pressures and stress. The eventual failure of these materials is typically due to a combination of heat weakening of the metal, wearing and corrosion, depending on the application. Metals used in applications such as firearm components (e.g., the barrel), internal combustion engines, deep sea drilling rigs, turbochargers, superchargers, high pressure pumps, structural metal (e.g., for high rise buildings, bridges, etc.) are all subjected to varying stresses that eventually lead to decreased strength or failure.
For example, it is known that firearm barrels become heated during use and such heating can lead to changes in the barrel that effect the accuracy or operation of the firearm. A firearm is a weapon that launches one, or many, projectile(s) at high velocity through confined burning of a propellant. The burning of the propellant fills the interior of an ammunition cartridge or the chamber of a firearm, leading to the expulsion of a bullet or shell. Heat produced by the burning propellant, as well as the heat produced by the projectile(s) are accelerated through the barrel, causes the temperature of the barrel to rise. As the temperature of the barrel rise, the barrel may change shape, changing the accuracy of the firearm and also loses some of its strength. If the firearm is being used to fire multiple projectiles at a rapid rate, the barrel will continue to heat up until, becoming softer and less accurate. If the heat is not properly dissipated by the barrel, the barrel will eventually undergo mechanical failure. The barrel, therefore, becomes the limiting factor for the rate at which projectiles can be fired from the firearm, and/or the velocity at which the projectiles are fired.
Metals and refractory materials may include a chromium coating. Chromium coatings reduce the friction between the components during operation. For example, in firearms, a chromium coating placed on the barrel bore will reduce the friction between the projectile and the barrel, producing less heat. A chromium coating may also provided increased resistance to corrosive materials.
Chrome is a heavy metal which is deposited onto the metal surface using, for example, aqueous electrodeposition. The chromic acid used in the deposition process is a hazardous substance and is a major problem when it comes to environmental pollution prevention efforts and worker safety. Hexavalent chromium, used in electrodeposition processes, is a known carcinogen which is difficult and expensive to dispose of.
It is desirable to have alternate coatings for metals and refractory materials that are not as toxic and are simpler to produce.